1. Field of the Invention
The present invention relates generally to optical communication systems and methods of operating such optical communication systems. More particularly, the present invention is directed towards systems and methods that employ non-revertive switching between a primary fiber associated with the optical communication system and a secondary fiber associated with the optical communication system.
2. Description of Related Art
Optical wavelength division multiplexing gradually has become the standard backbone network for fiber optic communication systems. Wavelength division multiplexing systems employ signals that consist of a number of different wavelengths, which are known as carrier signals or channels, to transmit information over optical fibers. Each carrier signal is modulated by one or more information signals. Consequently, a significant number information signals may be transmitted over a signal optical fiber using wavelength division multiplexing technology.
Fiber optic communication systems generally are arranged with a plurality of optical devices in any one of a number of topological configurations. The simplest configuration is two optical devices communicating data over an optical link. This configuration may be extended to a daisy-chain configuration in which three or more optical devices are connected in series by a plurality of optical links. In each of these fiber optic communication systems, the optical link between two optical devices generally includes a plurality of optical fibers, which allows for bidirectional communication between the optical devices, and provides redundancy in the event of a fault in one or more of the optical fibers.
In one known fiber optic communication system, an optical switch may be employed to switch communications between a first pair of optical devices from a primary optical fiber(s) to a protection optical fiber(s) when there is a fault associated with the primary optical fiber(s). This known protection scheme is a one-to-one protection scheme that requires duplicated hardware in the fiber optic communication system. Specifically, a second pair of optical devices are connected to the protection optical fiber(s), such that when there is a fault associated with the primary optical fiber(s) or a fault associated with one of the first pair of optical devices, the system switches from the primary optical fiber(s) to the protection optical fiber(s). Although this protection scheme is reliable because it protects against both optical fiber failure and hardware (optical device) failure, this protection scheme is expensive because it requires that the optical fiber system include duplicated hardware. Another known fiber optic communication system is a revertive protection scheme that does not duplicate hardware in the fiber optic communication system, but instead, only protects against fiber failure. However, this known revertive protection scheme has the disadvantage of using a 3 dB splitter, which has an associated 3 dB losses in optical power.